Abstract

This paper proposes an electrochemicaletching technique to fabricate tungsten tips. Tips combining well-defined conical shape, a length as large as 2 mm, and sharpness with a radius of curvature of around 20 nm are fabricated using the proposed technique. These tips are needed in a variety of applications including multipoint contact measurements and nanomanipulation. The technique consists of three steps: the first is static etching, which creates a neck-in phenomenon on the wire; the second is dynamic etching, where the wire is oscillated up and down in the solution to form a long conical shape; finally, static etching is applied again to break the wire, and thus, sharp tips are produced. The best operating conditions of the process were experimentally obtained. These factors include the position of the cathode, the length of the immersed wire, and the applied voltage. The effects of these factors on the etchingcurrent and tip fidelity were also examined based on the measuredetchingcurrent. In particular, the position of the cathode determines the strength of the electrical field near the air/solution interface; the immersed wire depth determines mainly the equivalent resistance of the process and thus controls the etchingcurrent; and the applied voltage defines the etching rate of the wire.

Received 07 January 2014Accepted 16 April 2014Published online 25 April 2014

Acknowledgments:

The authors would like to acknowledge Sailu Nemana and Eswar Prasad of Sensor Technology Limited for the insight they provided in establishing the experimental conditions and also acknowledge the financial support from the Ontario Research Fund—Research Excellence IV Program.